Dad ran "Big A" tires on his 6620 and 7720. They were 43 x 66 x 32. I sold them about 10 years ago, as they were to small for a 9600 (used 44 x 73 x 32 for the 9600).
The big tires were great for reduced ground pressure. Before we bought them in the mid '80's, we also had a "G" Gleaner. The G would go while the 7720 sat because the tracks were to deep. After we added the Big A tires to the JD, it went better in soft conditions than the Gleaner.
Dad also added duals to the rear of the JD, but I don't remember what he used. They were probably smooth tires with shop built spacers. IIRC, the power steering didn't handle the duals very well. If you forget bigger tires on the rear, the big ones on the front won't help.
The stubble stompers were available for the row crop heads. You just put them on the rows that the tires were running over. I think they were essential for cutting beans. In milo, they just lean the stalk over so the tire flattens it without injury.